Quote: johnggreen
Shallowskiff,
I have flown my Bravo for almost seven years now. I'm based in MS and my profile is that I rarely fly less than 500 NM each time I crank the engine. My children are all in NC, VA, DC area. One went to Northwestern, so Chicago used to be a regular trip as well. Factor in a couple of business trips to the likes of CO and/or FL each year and well, you know why I have the Bravo.
90% of the time it is my wife and me with weekend bags. With TKS full, we are at gross. Sometimes I have to download a little fuel so I have pretty much perfected the max range speed/range/power combo for my airplane and make a note of almost every flight in my airplane flight log which stays in the airplane. By the way; even with TKS, my Bravo cruises about 4-7 knots over book speeds at gross! Yea, I'm a lucky man.
ANYWAY: You asked a legitimate question and I do have the answers to a limit. The limit being is that I do not use high power settings. The TIO-540 AF1B is one of the lower horsepower TIO-540 varients so most of the cruise power settings given by the POH are well above 75%. All those figures are in your Lycoming owners manual and make for very interesting reading.
To give you a feeling for power percentages, depending on altiude and temperature, according to the LOM (Lyc owner's manual) 75% can come at as little as 2200 rpm and 30" of manifold pressure. 2400/30" puts out about 220 h.p. wich would be about 80%. These figures will also vary according to whether you use best power (1650) or peak TIT. I use best power 90% of the time.
As to where I fly. I try to fly from 13m to 17m. Never higher for safety reasons. I always file IFR and find that if I'm at 12m or higher center doesn't hand me off to the approach controls that I pass over which greatly reduces my workload.
So, here goes.
At 15,000 after climbing out at gross weight:
2,200/28", 13 gph, 175 knots true.
2,200/30" 15 gph, 180 true maybe a little more.
2400/30" 17 gmp 190 true maybe a little less.
Leaning to peak TIT at 2400/30 will reduce gph to 15. You will lose about 2-3 knots.
If I have to stay "down low" 10,000' for headwinds, I will use 2400/30" and get 180 true.
I am doing this from memory and if I checked my flight log might make some minor corrections, but that is close.
To get the higher speeds, you will have to run your engine at 85% plus settings. The time savings are minimal.
By the way, my CHT's rarely reach 360.
Anything else?
JG
